How big should that gap be?
The WHO recommends “3 feet”, the CDC recommends 6 feet, but new research shows they got the model wrong and we might need to be 30 feet apart. Not to mention that the cloud of aerosols can wander suspended for hours. So we may need to be 30 feet and three hours apart.
No wonder churches and places where people sing are such high risk events, and why an astonishing 12,000 health workers are infected with coronavirus in Spain.
They aren’t sure if their new findings have clinical implications, which says a lot about how much we don’t know. The 27 ft distance applies to sneezes, so if the other party isn’t sneezing you might not have to be so far. Lucky sneezing isn’t that common, though the dry cough is. Personal trainers at 27 feet is going to be tricky.
UPDATE: Some readers ask whether one new study is even worth reporting, accusing me of “scare tactics”. I’ve been reading medical papers now for over 20 years, so forgive me if I found the results here so banal that I didn’t mention that this result is barely new, and very well corroborated. Indeed it is not at all surprising to me that in some circumstances (right temp, humidity and airdraft) these viral particles would stay suspended for hours and travel much more than “6 feet”. In the last two months I’ve seen the same essential results posted by the CDC, Korean Profs, Chinese doctors and for anyone trained in microbiology, this is hardly news. I remain surprised that after ten years of being data driven in a field outside my training and primary interest, readers leap to declare astrological or political when I return to a field I got my degree in. I am still the same skeptic I always was. Stick with the data.
MIT associate professor Lydia Bourouiba, who has researched the dynamics of coughs and sneezes for years, warns in newly published research that the current guidelines are based on outdated models from the 1930s.
Rather than the assumed safety of 6 foot, Bourouiba warns that “pathogen-bearing droplets of all sizes can travel 23 to 27 feet.”
Her research, published in the Journal of the American Medical Association, also warns that “droplets that settle along the trajectory can contaminate surfaces” — and “residues or droplet nuclei” may “stay suspended in the air for hours.”
Droplets that settle along the trajectory can contaminate surfaces, while the rest remain trapped and clustered in the moving cloud. Eventually the cloud and its droplet payload lose momentum and coherence, and the remaining droplets within the cloud evaporate, producing residues or droplet nuclei that may stay suspended in the air for hours, following airflow patterns imposed by ventilation or climate-control systems.
In the latest World Health Organization recommendations for COVID-19, health care personnel and other staff are advised to maintain a 3-foot (1-m)6 distance away from a person showing symptoms of disease, such as coughing and sneezing. The Centers for Disease Control and Prevention recommends a 6-foot (2-m) separation.7,8 However, these distances are based on estimates of range that have not considered the possible presence of a high-momentum cloud carrying the droplets long distances.